1. Field of the Invention
The present invention generally relates to micro displacement mechanisms and, more particularly, to a micro displacement mechanism using a piezoelectric actuator and a magnetic disk apparatus, which causes a magnetic head to be minutely displaced by using such a micro displacement mechanism.
2. Description of the Related Art
With progress in miniaturization and precision of information equipments, a demand is increasing for an actuator, which can realize a micro displacement or movement with high accuracy. For example, a micro actuator, which can control a movement of a minute distance, has been required for a head actuator of an inkjet printer or a magnetic disk apparatus.
On the other hand, in a magnetic disk apparatus, with expansion of the market and high-performance of an apparatus, an increase in a recording capacity has become important more and more. Generally, a high-capacity magnetic disk apparatus can be achieved by increasing a memory capacity per disk. In order to achieve a high-density recording without changing a size of a disk, that is, a diameter of a disk, it is necessary to increase a number of tracks (TPI) per unit length, that is, reducing a width of a track. Thus, it is necessary to increase a position accuracy of a head in a direction of a track width, and it is desirous to develop a micro actuator for a magnetic head, which is capable of performing positioning with high accuracy.
A coerce actuator in a fixed part of a suspension holding a head (slider) has been used for conventional head positioning. Conventionally, such a method sufficiently covers recording density of a medium. However, due to high-densification of recording density associated with an increase in a capacity of a recording apparatus, the conventional method has become insufficient in positioning accuracy of a head, and there may occur a read or write error of a head.
Thus, as measures for improving a positioning accuracy of a head, there is suggested a structure in which a micro actuator, which directly displaces a slider, is arranged between the slider and a suspension (for example, refer to Patent Documents 1 and 2). The micro actuator is capable of displacing a head attached to an extreme end of an arm independently of an action of a coerce actuator.
Patent Document 1: Japanese Laid-Open Patent Application No. 2001-327178
Patent Document 2: Japanese Laid-Open Patent Application No. 2003-284362
The micro-actuators disclosed in the above-mentioned Patent Documents 1 and 2 have a structure in which a piezoelectric actuator is disposed between a slider and a suspension so as to minutely displace the slider relative to the suspension. In this structure, a thickness of the slider part is increased due to a portion corresponding to the actuator. Accordingly, when this structure is applied to a magnetic disk apparatus having a plurality of disks in a stacked state, an additional space is required between the magnetic disks since the piezoelectric actuator and the slider are disposed between the adjacent magnetic disks. Thus, there is a problem in that the thickness of the magnetic disk apparatus is increased or a number of disks in the magnetic disk apparatus is limited.